The present invention relates to a system for a four-wheel drive vehicle for automatically controlling transmission torque to rear-wheel.
During the driving of the four-wheel drive vehicle, an amount of tire scraping occurs because of slight differences in effective wheel radii caused by inevitable differences in tire inflation, tread wear or variation in loading. In addition, when the vehicle negotiates corners, braking phenomenon called "tight corner braking" will occur at a sharp corner. This is caused by the reason that the front wheels run through an arc of greater radius than that of the rear wheels and therefore tend to rotate faster than the rear wheels. This will result in increase of tire wear and fuel consumption and decrease of driveability.
In order to eliminate such disadvantages, a four-wheel drive vehicle provided with a friction clutch system having a variable transmission torque has been proposed. Generally, the transmission torque is controlled in dependency on the steering angle, causing the slip in the friction clutch to prevent the tight corner braking.